One of the inherent problems introduced in communication networks supporting mobile/wireless connections is the fact that a user's access point to the wired network is not static and user movement restfits in handoff events from one access point to another. When an access point needs to be changed as a result of the movement of the mobile unit, the packets (or frames) destined to the mobile terminal need to be routed to the new access point with which the mobile user has established a connection.
Network routing requires routing (or switching) equipment and a set of rules which govern the forwarding of packets from one port of the router to another. The protocol entities that are routed through the network can be packets which belong to the network layer which is the layer three of the OSI (Open System Interconnection) reference model, or these entities can be frames which belong to the data link layer or layer two in the OSI reference model. In the latter case, the switching equipment arc often called bridges. One important and widely used routing scheme is source routing. In this scheme, the packet (or frame) contains the whole routing information in a field which is called the routing information field (RIF). Essentially, the RIF of each packet (or frame) contains the logical address of all switching points (routers or bridges) and/or the network or LAN segment ID along the route of the packet. The sequence of these addresses decline the path that each packet (or frame) takes from its entry point to the network to its final destination. There are many ways to find a path or route through the network at connection setup time. One example is the single/all route broadcast used in IBM's token ring networks which uses source routing as means of transporting packets through bridged local area network consisting of token rings and source routing bridges. Usually, a route is discovered for every destination is saved or cached in the local memory of the station, and used for every packet (or frame) that is sent to that destination. Reference [1] teaches the establishment of a route using a route discovery mechanism in a source routing network; however the reference does not deal with the situation when one of the parties is a mobile device in motion.
In a network where source routing is used, the packet (or frame) originator communicating to a mobile terminal which has completed a hand-off needs to discover a new route to the new access point and use a new set of addresses in the RIF in order to reroute its packets to the new access point. This would involve changes to the network operating system of that originator.